Sea urchin-like NiCoO₂@C nanocomposites for Li-ion batteries and supercapacitors

The rational construction of battery electrode architecture that offers both high energy and power densities on a gravimetric and volumetric basis is a critical concern but achieving this aim is beset by many fundamental and practical challenges. Here we report a new sea urchin-like NiCoO₂@C composite electrode architecture composed of NiCoO₂ nanosheets grown on hollow concave carbon disks. Such a unique structural design not only preserves all the advantages of hollow structures but also increases the packing density of the active materials. NiCoO₂ nanosheets grown on carbon disks promote a high utilization of active materials in redox reactions by reducing the path length for Li⁺ ions and for electron transfer. Meanwhile, the hollow concave carbon not only reduces the volume change, but also improves the volumetric energy density of the entire composite electrode. As a result, the nanocomposites exhibit superior electrochemical performance measured in terms of high capacity/capacitance, stable cycling performance and good rate capability in both Li-ion battery and supercapacitor applications. Such nanostructured composite electrode may also have great potential for application in other electrochemical devices.